The Nation's Two Crime Measures

The U.S. Department of Justice administers two statistical programs to measure the
magnitude, nature, and impact of crime in the Nation: the Uniform Crime Reporting
(UCR) Program and the National Crime Victimization Survey (NCVS). Each of these
programs produces valuable information about aspects of the Nation’s crime problem.
Because the UCR and NCVS programs are conducted for different purposes, use different
methods, and focus on somewhat different aspects of crime, the information they
produce together provides a more comprehensive panorama of the Nation’s crime
problem than either could produce alone.

Uniform Crime Reports

The UCR Program, administered by the FBI, began in 1929 and collects information on
the following crimes reported to law enforcement authorities: murder and nonnegligent
manslaughter, forcible rape, robbery, aggravated assault, burglary, larceny-theft, motor
vehicle theft, and arson. Law enforcement agencies report arrest data for 21 additional
crime categories.

The UCR Program compiles data from monthly law enforcement reports or individual
crime incident records transmitted directly to the FBI or to centralized state agencies
that then report to the FBI. The program thoroughly examines each report it receives for
reasonableness, accuracy, and deviations that may indicate errors. Large variations in
crime levels may indicate modified records procedures, incomplete reporting, or changes
in a jurisdiction’s boundaries. To identify any unusual fluctuations in an agency’s crime
counts, the Program compares monthly reports to previous submissions of the agency
and with those for similar agencies.

The UCR Program presents crime counts for the Nation as a whole, as well as for regions,
states, counties, cities, towns, tribal law enforcement, and colleges and universities. This
permits studies among neighboring jurisdictions and among those with similar
populations and other common characteristics.

The FBI annually publishes its findings in a preliminary release in the spring of the
following calendar year, followed by a detailed annual report, Crime in the
United States, issued in the fall. In addition to crime counts and trends, this report
includes data on crimes cleared, persons arrested (age, sex, and race), law enforcement
personnel, and the characteristics of homicides (including age, sex, and race of victims
and offenders; victim-offender relationships; weapons used; and circumstances
surrounding the homicides). Other periodic reports are also available from the UCR
Program.

The state and local law enforcement agencies participating in the UCR Program are
continually converting to the more comprehensive and detailed National Incident-Based
Reporting System (NIBRS). The NIBRS provides detailed information about each
criminal incident in 22 broad categories of offenses.

National Crime Victimization Survey

The Bureau of Justice Statistics (BJS) NCVS, which began in 1973, provides a detailed
picture of crime incidents, victims, and trends. After a substantial period of research, the
BJS completed an intensive methodological redesign of the survey in 1993. The BJS
conducted the redesign to improve the questions used to uncover crime, update the
survey methods, and broaden the scope of crimes measured. The redesigned survey
collects detailed information on the frequency and nature of the crimes of rape, sexual
assault, personal robbery, aggravated and simple assault, household burglary, theft, and
motor vehicle theft. It does not measure homicide or commercial crimes (such as
burglaries of stores).

Two times a year, the U.S. Census Bureau personnel interview household members in a
nationally representative sample of approximately 43,000 households (about 76,000
people). Approximately 150,000 interviews of persons age 12 or older are conducted
annually. Households stay in the sample for 3 years. New households rotate into the
sample on an ongoing basis.

The NCVS collects information on crimes suffered by individuals and households,
whether or not those crimes were reported to law enforcement. It estimates the
proportion of each crime type reported to law enforcement, and it summarizes the
reasons that victims give for reporting or not reporting.

The survey provides information about victims (age, sex, race, ethnicity, marital status,
income, and educational level), offenders (sex, race, approximate age, and victim-
offender relationship), and the crimes (time and place of occurrence, use of weapons,
nature of injury, and economic consequences). Questions also cover the experiences of
victims with the criminal justice system, self-protective measures used by victims, and
possible substance abuse by offenders. Supplements are added periodically to the survey
to obtain detailed information on topics like school crime.

The BJS published the first data from the redesigned NCVS in a BJS bulletin in June
1995. BJS publication of NCVS data includes Criminal Victimization in the United
States, an annual report that covers the broad range of detailed information collected by
the NCVS. The BJS publishes detailed reports on topics such as crime against women,
urban crime, and gun use in crime. The National Archive of Criminal Justice Data at the
University of Michigan archives the NCVS data files to enable researchers to perform
independent analyses.

Comparing UCR and the NCVS

Because the BJS designed the NCVS to complement the UCR Program, the two programs
share many similarities. As much as their different collection methods permit, the two
measure the same subset of serious crimes, defined alike. Both programs cover rape,
robbery, aggravated assault, burglary, theft, and motor vehicle theft. Rape, robbery,
theft, and motor vehicle theft are defined virtually identically by both the UCR and the
NCVS. (Although rape is defined analogously, the UCR Program measures the crime
against women only, and the NCVS measures it against both sexes.)

There are also significant differences between the two programs. First, the two programs
were created to serve different purposes. The UCR Program’s primary objective is to
provide a reliable set of criminal justice statistics for law enforcement administration,
operation, and management. The BJS established the NCVS to provide previously
unavailable information about crime (including crime not reported to police), victims,
and offenders.

Second, the two programs measure an overlapping but nonidentical set of crimes.
The NCVS includes crimes both reported and not reported to law enforcement. The
NCVS excludes, but the UCR includes, homicide, arson, commercial crimes, and crimes
against children under age 12. The UCR captures crimes reported to law enforcement
but collects only arrest data for simple assault and sexual assault other than forcible rape.

Third, because of methodology, the NCVS and UCR definitions of some crime differ. For
example, the UCR defines burglary as the unlawful entry or attempted entry of a
structure to commit a felony or theft. The NCVS, not wanting to ask victims to ascertain
offender motives, defines burglary as the entry or attempted entry of a residence by a
person who had no right to be there.

Fourth, for property crimes (burglary, theft, and motor vehicle theft), the two programs
calculate crime rates using different bases. The UCR rates for these crimes are per capita
(number of crimes per 100,000 persons), whereas the NCVS rates for these crimes are
per household (number of crimes per 1,000 households).

Because the number of households may not grow at the same rate each year as the total
population, trend data for rates of property crimes measured by the two programs may
not be comparable. In addition, some differences in the data from the two programs
may result from sampling variation in the NCVS and from estimating for nonresponse in
the UCR.

The BJS derives the NCVS estimates from interviewing a sample. The estimates are,
therefore, subject to a margin of error. The BJS uses rigorous statistical methods to
calculate confidence intervals around all survey estimates. The BJS describes trend data
in the NCVS reports as genuine only if there is at least a 90 percent certainty that the
measured changes are not the result of sampling variation. The UCR Program bases its
data on the actual counts of offenses reported by law enforcement agencies. In some
circumstances, the UCR Program estimates its data for nonparticipating agencies or
those reporting partial data. Apparent discrepancies between statistics from the two
programs can usually be accounted for by their definitional and procedural differences or
resolved by comparing NCVS sampling variations (confidence intervals) of those crimes
said to have been reported to police with UCR statistics.

For most types of crimes measured by both the UCR and NCVS, analysts familiar with
the programs can exclude from analysis those aspects of crime not common to both.
Resulting long-term trend lines can be brought into close concordance. The impact of
such adjustments is most striking for robbery, burglary, and motor vehicle theft, whose
definitions most closely coincide.

With robbery, the BJS bases the NCVS victimization rates only on robberies reported to
the police. It is also possible to remove UCR robberies of commercial establishments
such as gas stations, convenience stores, and banks from analysis. When users compare
the resulting NCVS police-reported robbery rates and the UCR noncommercial robbery
rates, the results reveal closely corresponding long-term trends.

Each program has unique strengths. The UCR provides a measure of the number of
crimes reported to law enforcement agencies throughout the country. The UCR’s
Supplementary Homicide Reports provide the most reliable, timely data on the extent
and nature of homicides in the Nation. The NCVS is the primary source of information
on the characteristics of criminal victimization and on the number and types of crimes
not reported to law enforcement authorities.

By understanding the strengths and limitations of each program, it is possible to use the
UCR and NCVS to achieve a greater understanding of crime trends and the nature of
crime in the United States. For example, changes in police procedures, shifting attitudes
towards crime and police, and other societal changes can affect the extent to which
people report and law enforcement agencies record crime. NCVS and UCR data can be
used in concert to explore why trends in reported and police recorded crime may differ.